Typical thermoplastic synthetic fibers such as nylon or polyester fibers are melted at about 250° C. However, a decomposition temperature of heat resistant high performance fibers such as aramid fibers, wholly aromatic polyester fibers, and polyparaphenylene-benzobisoxazole fibers is high to be about 500° C.
The heat resistant high performance fibers have excellent heat resistant and flame retardancy, thus being extensively used in fire fighting garments, racer's suits, steel worker's clothes, and welder's clothes at high risk of exposure to flames and high temperatures. Further, the heat resistant high performance fibers may have heat resistance and high tenacity, thus being frequently used in athlete's uniforms, working clothes, ropes, tire cords, and others requiring high tear tenacity and heat resistance.
However, a yarn made of typical heat resistant high performance fibers has little elasticity, and fabrics made based on the fibers have little elasticity, too. Therefore, when clothes made of the heat resistant fiber-based fabrics were put on, the sense of wearing is not favorable, and there is a limit in activity required at exercise or work.
Accordingly, various studies have been conducted to provide elasticity to the yarns or the fabrics using the heat resistant fibers, and the resulting products are released. However, most of the current study results and released products are accompanied by deterioration in function of the heat resistant fibers due to heat treatment at high temperatures. Moreover, there are many cases that elasticity provided to the yarns or the fabrics using the heat resistant fibers is weak.